Downhole production boreholes utilized in subterranean operations typically utilize casings disposed therein to protect the borehole from downhole pressures, chemical reactions and other conditions and prevent failures such as borehole collapse, burst and tensile failures. Casings can also be used to define production zones in various portions of the borehole.
Casing monitoring and evaluation techniques are important tools in maintaining the integrity of the casing, and in turn maintaining the integrity of the borehole. Typical evaluation and maintenance procedures involve interrogating the casing and cement that is used to bond the casing to a borehole wall to determine whether voids are present between the casing and the borehole wall.
Typical methods for detecting voids include interrogating the casing and cement with acoustic signals to detect micro annuluses and other openings formed between the casing and the borehole wall. Detected microannuluses are typically corrected via methods such as applying hydrostatic pressure to the interior of the casing. Such detection methods can be inefficient and inaccurate in that they may be unable to effectively differentiate between an insignificant microannulus and a true void between the casing and the cement that can compromise the hydraulic seal formed therebetween.